The present invention relates to easily tearable laminated barrier film capable of being split easily and bag products using the film, which can be used, for instance, as wrapping bag of food, medicine, industrial products etc.
Conventionally, polyvinylidene chloride (PVDC) has been generally used as wrapping material of ham and sausage.
However, polyvinylidene chloride has a problem of generating chloride gas when being burnt. On account of recently growing concern over environmental problems, other wrapping material not causing environmental pollution is requested in the field where such chloride resin has been used.
In addition, when conventional wrapping material is made into a bag, high-frequency sealer capable of high-temperature sealing is required.
Further, the wrapping material using conventional wrapping material cannot be easily torn by hand in opening the bag.
Furthermore, as a casing of sausage, top and bottom sides thereof are generally tacked by a metal band such as aluminum. However, since the casing includes the metal band, a metal locator cannot detect foreign body.
Accordingly, an object of the present invention is to provide an easily tearable laminated barrier film which is harmless to the environment and has an easy-tearability and appropriate barrier property, and bag products using the film.
Easily tearable laminated barrier film according to first aspect of the present invention includes: an easily tearable barrier film including first, second and third layers, the easily tearable barrier film having orientation ratio of not less than 2.8 in both machine direction (drawing direction of the film) and transverse direction (width direction of the film) during orientation and shrinkage factor of 15 to 40% in pressurized 120xc2x0 C. hot water for twenty minutes by heat stabilization at 120 to 195xc2x0 C. heat treatment temperature; and at least one base film laminated on the easily tearable barrier film. The easily tearable laminated barrier film is characterized in that respective layers of the easily tearable barrier film being constituted so that the first and the third layer contain 60 to 85 wt % of nylon6 (Ny6), 15 to 40 wt % of metaxylylene adipamide (MXD6), and 0.1 to 10 wt % of modifier (respective compositions totaling 100 wt %) and so that the second layer contains 0 to 40 wt % of thermoplastic resin, 60 to 95 wt % of MXD6, and 0.1 to 10 wt % of modifier (respective compositions totaling 100 wt %), the modifier being at least one selected from polyamide elastomer (PAE) and modified EVA, the modified EVA being an acid denatured body of partial saponification material of ethylene-vinyl acetate copolymer having 20 to 50 wt % of vinyl acetate.
When the first and the third layer have less than 15 wt. % of MXD6, easy tearability does not come out. On the other hand, when MXD6 exceeds 40 wt %, impact strength is greatly reduced, thus deteriorating practicability. Preferably, the content of MXD6 is 20 to 40 wt. %.
General polyolefin, polyester, polyamide etc. can be used as the thermoplastic resin of the second layer. Polyamide is most preferably used among them, and, especially, nylon6 (Ny6) is most suitably used therefor.
When MXD6 is less than 60 wt % in the second layer, barrier property is deteriorated. On the other hand, when exceeding 95 wt %, shrinkage factor can get worse. 70 to 85 wt % of MXD6 is preferably contained therein.
When the content of modifier is less than 0.1 wt % in the first to the third layer, pinholes are likely to be generated. On the other hand, when the content of the modifier exceeds 10 wt %, optical property of the film can be deteriorated to reduce value of the product.
The easily tearable film can be manufactured by melting and kneading material including predetermined amount of Ny6, MXD6 and modifier, extruding the material from a die in a film shape, cooling the film, and orienting the formed raw film at a ratio more than 2.8 in both machine direction and transverse direction.
When the orientation ratio is less than 2.8, easy tearability and linear cut property are deteriorated. Further, impact strength can be reduced, thus causing problems in actual use. Preferably, the orientation ratio is more than or the same as 3.0.
The orientation process is preferably conducted by simultaneous biaxial orientation according to tubular method.
When the heat treatment temperature is less than 120xc2x0 C., shrinkage properties can be too great, thus causing wrinkles or the like on account of moisture absorption during storage and transportation to be unstabilized.
When the heat treatment temperature exceeds 195xc2x0 C., crystallization of the film is too advanced, thus lowering its shrinkage rate at a target temperature. Further, a wrapping material after being filled cannot be sufficiently shrinked, thus deteriorating its appearance.
When the shrinkage rate in 120xc2x0 C. pressurized hot water is less than 15%, shrinkage rate as the wrapping material is insufficient and adhesion with the contents is deteriorated. When the shrinkage rate exceeds 40%, since the shrinkage rate is too great and wrapping form is collapsed, appearance of the products can be deteriorated. The condition of 120xc2x0 C. hot water for twenty minutes is in compliance with a condition for heat pasteurizing (retorting) sausages etc. after being filled in the bag.
The modified EVA can be manufactured as follows.
Material EVA may be manufactured according to any known manufacturing method such as high-pressure process and emulsification process. Normally, EVA containing 20 to 50 wt % of vinyl acetate is used, and EVA containing 30 to 45 wt % of vinyl acetate is preferably used.
Subsequently, the EVA is treated by a known saponification method, such as treating the EVA with a system including low boiling-point alcohol (such as methanol and ethanol) and alkali (such as sodium hydroxide, potassium hydroxide and sodium methylate) for obtaining partial saponification material of EVA having 50 to 95 mole percent saponification degree.
Next, the partial saponification material is processed using graft reaction and esterification reaction to obtain acid denatured body of EVA partial saponification material. The acid denaturation is mainly for applying affinity to polyamide.
An easily tearable laminated barrier film according to second aspect of the present invention is characterized in, in the first aspect of the present invention, that the thermoplastic resin of the second layer contains 5 to 40 wt % of nylon6 (Ny6).
When content of Ny6 as the thermoplastic resin of the second layer is less than 5 wt %, anti-pinhole property and shrinkage rate increase becomes insufficient. On the other hand, when the content of Ny6 exceeds 40 wt %, gas barrier property can be deteriorated.
Ny6 is contained in the resin of the second layer as well as MXD6 and modifier for improving anti-pinhole property and shrinkage rate.
Ny6 as the thermoplastic resin of the second layer is preferably 10 to 30 wt %, more preferably 20 to 30 wt %.
An easily tearable laminated barrier film according to third aspect of the present invention is characterized in, in the first or the second aspect of the present invention, that layer ratio between the first or the third layer and the second layer is from 1:8 to 2:1. In this case, layer ratio of the first, the second, and the third layer is preferably from 1:8:1 to 4:2:4.
When the ratio of the respective layers is out of the above range, easy tearability, anti-pinhole property, gas barrier property and optical property can be deteriorated.
An easily tearable laminated barrier film according to fourth aspect of the present invention is characterized in, in any one of the first to third aspect of the present invention, that the base film is a sealant film.
As a material of the sealant film, L-LDPE (linear low-density polyethylene), LDPE (low-density polyethylene), HDPE (high-density polyethylene), CPP (cast polypropylene), EVA (ethylene-vinyl acetate copolymer), PB (polybutene-1), ionomer, PMMA (polymethyl methacrylate), EMAA (ethylene-co-methacrylic acid copolymer), EAA (ethylene-acrylic acid copolymer), EMMA (ethylene-methacrylate methyl copolymer) and compounds thereof can be suitably used.
When the base film laminated on one side of the easily tearable barrier film is a sealant film, material of the other base film laminated on the other side can be determined at will.
The material of the other base film may be biaxially oriented and mono-axially oriented film or cast film such as PET (polyethylene terephthalate), EVOH (ethylene-vinylalcohol copolymer), PVA (polyvinyl alcohol), PP (polypropylene), Ny (nylon), HDPE (high-density polyethylene), PS (polystyrene) as well as material of the sealant film.
Incidentally, necessary additive may be contained in the laminated film of the present invention.
For such additive, anti-blocking agent (such as inorganic filler), water-repellant (such as ethylene bis-stearate), lubricant (such as calcium stearate) may preferably be used.
The laminated films may be laminated by, for instance, extrusion laminate, hot melt laminate, dry laminate, and wet laminate methods.
A bag product according to fifth aspect of the present invention is manufactured with use of the easily tearable laminated barrier film according to any one of the first to fourth aspects of the present invention.
On account of shrinkage property thereof, the bag product can be suitably used for wrapping foods such as ham, sausage and daily dish.